1. Field of the Invention
The present invention relates in general to a powder metal engine component, and more particularly to a new and improved powder metal valve seat insert useful in both light and heavy duty internal combustion engine applications.
2. Description of the Related Art
The operation cycle of an internal combustion engine is well known in this art. The physical requirements for the intake and exhaust valves, valve guides and valve seat inserts to effectively interact in sealing the combustion have been studied extensively. Still engine and vehicle manufacturers constantly seek ways to meet more stringent wear and cost reduction challenges in manufacturing engine components for providing cost-effective engines that operate longer. Powder metallurgy has recently been employed in the manufacture of engine components and permits latitude in selecting a variety of metallic or even ceramic compositions as well as offering design flexibility. The powder metallurgy process is a highly developed method of manufacturing ferrous and nonferrous parts. Some advantages of the powder metallurgy process include but are not limited to minimizing scrap losses, minimizing machining, maintaining close dimensional tolerances, providing materials with a controlled porosity for self-lubrication or infiltration, and manufacturing complex shapes.
Valve seat inserts for internal combustion engines require high wear resistance materials for operation at elevated temperatures for prolonged periods of time. Additionally, valve seat inserts require high creep strength and high thermal fatigue strength even under repeated impact loading at elevated temperatures. Typically, the valve seat insert materials that are made from high alloy powders have low compressibility. Therefore, processes such as double pressing, double sintering, high temperature sintering, copper infiltrating, and hot forging are used to achieve a desired density level. Unfortunately, these additional steps can make the material prohibitively expensive. Internal combustion engines can operate on a wide variety of fuels, for example, gasoline, both leaded or unleaded fuel, diesel, or alternative fuels such as CNG (compressed natural gas). The heavy duty or truck engine applications operate at even higher combustion pressure than in light duty or passenger car applications and so require even better wear resistance materials. It is further known that exhaust valve seat inserts operate under more elevated temperatures than intake valve seat inserts. To provide all of the different types of valve seat inserts for these wide variety of applications becomes technically impractical and economically burdensome.
It is known that wear resistance, both abrasive and adhesive, are prime requirements for valve seat inserts used in internal combustion engines. In an effort to achieve a combination of good heat and corrosion resistance and machinability coupled with good wear resistance, valve seat inserts have been made from cobalt, nickel, or martensite iron based alloy castings. These alloys have been generally preferred over austenitic heat-resistance steels with high chromium and nickel content because of the presence of wear resistant carbides in the cast alloys. However, the cobalt or nickel based alloys are typically more expensive.
Thus, there still exists a need for a new powder metal engine component, and particularly a valve seat insert suitable for most internal combustion engine applications for both exhaust and intake valves whether in a heavy duty truck application or a lighter application such as in a passenger car. Preferably, such a powder metal valve seat insert may be used with any type of internal combustion engine fuel including, but not limited to, gasoline, leaded or unleaded, diesel, or any alternative fuel like natural gas. The powder metal valve seat insert should exhibit superior properties of abrasive and adhesive wear resistance against various types of valve materials.
Accordingly, an object of the present invention is to provide a new powder metal engine component for an internal combustion engine.
Another object of the present invention is to provide a new powder metal valve seat insert that is suited for use in a wide variety of internal combustion engine applications.
Still another object of the present invention is to provide an improved powder metal valve seat insert particularly suited for operation in heavy duty truck engine applications.
Still another object of the present invention is to provide an improved powder metal valve seat insert suited for operation in an internal combustion engine capable of operating on any of a variety of fuels including, but not limited to, gasoline, both leaded or unleaded fuel, diesel, or an alternative dry fuel such as CNG, alcohol based fuel or mixtures thereof.
Still a further object of the present invention is to provide an improved powder metal valve seat insert that has superior properties in hardness, hot hardness, abrasive and adhesive wear resistance.
The above and other objects of the present invention are accomplished with an improved powder metal engine component comprising a material alloy similar in composition to Tribaloy alloys, in particular either a cobalt or iron based alloy, containing an intermetallic phase such as a Laves phase. Tribaloy is a registered trademark of Deloro Stellite Inc. The iron based powder metal engine component in accordance with the present invention comprises a chemical composition on a weight percent basis carbon (C) in an amount ranging from about 0.5 to about 1.5%; chromium (Cr) in an amount ranging from about 1.0 to about 4.0%; molybdenum (Mo) in an amount ranging from about 2.0 to about 8.0%; manganese (Mn) in an amount ranging from about 0.2 to 0.9%; vanadium (V) in an amount ranging from about 0.1 to about 0.8%; copper (Cu) in an amount ranging from about 0 to about 20.0%; nickel (Ni) in an amount ranging from about 0.2 to about 3.5%; sulfur (S) in an amount ranging from about 0.2 to about 0.8%; tungsten (W) in an amount ranging from about 0.2 to about 0.6% and the balance being substantially iron (Fe).
An alternate embodiment of the powder metal component in accordance with the present invention comprises a chemical composition on a weight percent basis carbon (C) in an amount ranging from about 0.7 to about 1.4%; chromium (Cr) in an amount ranging from about 1.0 to about 4.0%; molybdenum (Mo) in an amount ranging from about 6.0 to about 12.0%; silicon (Si) in an amount ranging from about 0.1 to about 1.0%; nickel (Ni) in an amount ranging from about 0.5 to about 3.5%; sulfur (S) in an amount ranging from about 0.2 to about 1.0%; cobalt (Co) in an amount ranging from about 4.0 to about 15.0%; copper (Cu) in an amount ranging up to about 20%; and the balance being substantially iron (Fe).